Voter-approved Local Option Transportation Sales Taxes (LOSTs) are a major source of revenue for transportation programs in California. LOSTs list projects and programs for voter approval that are to be implemented over long periods of time, often twenty or more years. To respond to changing conditions, agencies often need to amend voter-approved plans. Implementing agencies must be accountable to voters, balancing the need to fulfill commitments made against needs that change over time. Using the text of ballot measures, public utility codes, periodic agency reports, and case studies that included interviews of public officials, this study examines, provisions regarding accountability in California LOSTs, and procedures for amending proposed expenditures. It also reviews lawsuits brought in relation to accountability and plan amendments. It analyzes the ways in which California counties achieve needed flexibility within a framework that demands accountability to the voters. Requirements and patterns differ among counties, but most measures have been adapted to changing circumstances.